The introduction of device to device (D2D) technology provides technology support for increasing efficiency of use of frequency spectrum, increasing system throughput, reducing consumption of user equipment, and reducing operating cost of operators. The present 3GPP network has already studied the D2D technology, and defines multiple application scenarios of the D2D technology. In the study of the present D2D technology of the network-side, the main concern is the method of establishing a D2D network on the physical layer, for example, how to establish the D2D network between two user equipment.